EPOW - Ecology Picture of the Week

10-frame animation of forest fragmentation,
Upper Amazon Basin, Northeast Bolivia

Explanation:   This week we are flying over northeast Bolivia in the Upper Amazon of South America.  We are witnessing a lesson in how this tropical rainforest has become increasingly fragmented and converted to non-forest conditions.  

Our tiny 4-seater plane takes us from the heart of the Amazon rainforest along the border with Brazil over unbroken forest canopy ... over forests newly accessed by unpaved roads for slash and burn agriculture ... leading to more intensive agriculture and loss of soil nutrients from permanent leaching of nutrients (soil "laterization") ... to a landscape where most of the forest has been converted to agriculture, pasture, and human habitations.  

Forest "fragmentation" refers to the breaking up of forest cover to smaller patches, where the landscape has far more openings and edges between forest and non-forest than it would naturally.  

Animated sequence of false-color satellite imagery
of forest fragmentation around the city of Santa Cruz,
Bolivia, in the Upper Amazon Basin, from 1984 to 1998.
Dark green areas are the original extensive forest cover,
and light green and pink areas are agricultural and urban
areas devoid of primary forest cover.

Forest fragmentation in the tropics is a concern for conservation because it introduces exotic, invasive, weedy species of plants and animals into the remaining forest from along roadways and edges ... because it reduces the amount and quality of "interior" habitat of forests for species such as primates that require such undisturbed environments ... and because it sets the stage for further degradation and loss of forests if there are no checks on human sprawl.

Complicating -- and perhaps triggered by -- human-caused forest fragmentation is local change in patterns of climate, weather, and disturbance events such as fire.  Extensive forests can help to moderate weather extremes.  When forests are fragmented, the question arises as to which trees, other species, and ecosystems can be truly sustainable under such changing environmental conditions.  For example, perhaps only the more fire-prone trees and disturbance-tolerant wildlife will endure.  

False-color satellite image of the landscape near
Santa Cruz, Bolivia, showing major conversion and
fragmentation of native forest.  In this image, 
dark red is dense forest cover, and pink and white are 
where forest has been cleared for cropland and pasture.